Expandable interspinous process spacer implant

ABSTRACT

An expandable interspinous spacer implant that is configured to be inserted into an interspinous space that is defined between a spinous process of a superior vertebral body and a spinous process of an inferior vertebral body is provided. The implant may include a superior housing, an inferior housing, and a distracting member. The superior housing may have an outer surface that is configured to engage the spinous process of the superior vertebral body and the inferior housing may have an outer surface that is configured to engage the spinous process of the inferior vertebral body. The distracting member may be disposed between the superior and inferior housings, such that activation of the distracting member distracts the superior and inferior housings apart from each other.

BACKGROUND

A human vertebrae has a rearward projecting portion known as a spinousprocess. Bending of the spine can cause the spinous processes ofadjacent vertebrae to be moved toward each other. This constricts thespace in the spinal canal and foramina thereby causing pain. Suchconstriction, which is known as stenosis, can be treated by the use ofan implant in the space between adjacent spinous processes.

Some current implants are made of separate pieces which requireinsertion from opposite sides of the spine and in a posterior approachand necessitate rather wide openings into a patient, cutting both leftand right thoracolumbar fascia as well as stripping the multifidusmuscles from their attachments. It is desirable to provide an implantfor insertion between the spinous processes of adjacent vertebrae whichcan be inserted through a single opening and may be held firmly inposition between the vertebrae.

SUMMARY

An expandable interspinous spacer implant that is configured to beinserted into an interspinous space that is defined between a spinousprocess of a superior vertebral body and a spinous process of aninferior vertebral body is provided. The implant may include a superiorhousing, an inferior housing, and a distracting member. The superiorhousing may have an outer surface that is configured to engage thespinous process of the superior vertebral body and the inferior housingmay have an outer surface that is configured to engage the spinousprocess of the inferior vertebral body. The distracting member may berotatably disposed between the superior and inferior housings. Thedistracting member may define a first pair of opposed surfaces thatdefine a first distance therebetween, and a second pair of opposedsurfaces angularly offset with respect to the first pair of opposedsurfaces. The second pair of opposed surfaces may define a seconddistance therebetween that is greater than the first distance.

In another embodiment the implant may include a superior housing, aninferior housing, and a deployable wing member. The superior housing mayhave an outer surface configured to engage the spinous process of thesuperior vertebral body. The inferior housing may have an outer surfaceconfigured to engage the spinous process of the inferior vertebral body.The deployable wing member may be rotatably coupled to the superiorhousing and translatably guided through a slot defined by the inferiorhousing.

In another embodiment the implant may include a superior housing, aninferior housing, a distracting member, and at least one deployable wingmember. The superior housing may have an outer surface configured toengage the spinous process of the superior vertebral body. The inferiorhousing may have an outer surface configured to engage the spinousprocess of the inferior vertebral body. The distracting member may bedisposed between the superior and inferior housings. Movement of thedistracting member from a first position to a second position distractsthe superior and inferior housings apart from each other. The at leastone wing member includes an extension, and is rotatably coupled to arespective one of the superior and inferior housings, such that movementof the distraction member from the first position to the second positioncauses the at least one wing member to rotate about the respectivehousing to thereby cause the extension to extend out a respectivehousing.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofillustrative embodiments of the instrument of the present application,will be better understood when read in conjunction with the appendeddrawings. For the purposes of illustrating the interspinous spacerimplant of the present application, there is shown in the drawingsillustrative embodiments. It should be understood, however, that theapplication is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1 is a perspective view of an expandable interspinous processspacer implant in accordance with one embodiment after it has beeninserted into a space defined between adjacent spinous processes;

FIG. 2 is a perspective view of the expandable interspinous processspacer implant shown in FIG. 1, in a collapsed configuration;

FIG. 3A is a perspective view of the expandable interspinous processspacer implant of FIG. 2, with a superior first lateral side cover plateand an inferior first lateral side cover plate removed;

FIG. 3B is a perspective view of the expandable interspinous processspacer implant of FIG. 2, with a superior second lateral side coverplate and an inferior second lateral side cover plate removed;

FIG. 4 is a perspective view of the expandable interspinous processspacer implant of FIG. 2 in an expanded configuration;

FIG. 5 is a rear end elevational view of the expandable interspinousprocess spacer implant of FIG. 2 in an expanded configuration;

FIG. 6 is a rear cross sectional view of the expandable interspinousprocess spacer implant of FIG. 2 in a collapsed configuration;

FIG. 7A is a perspective view of the expandable interspinous processspacer implant of FIG. 2 being inserted into a space defined betweenadjacent spinous processes;

FIG. 7B is a perspective view of the expandable interspinous processspacer implant of FIG. 7A, after the spacer has been fully inserted intothe space defined between the adjacent spinous processes;

FIG. 7C is a perspective view of the expandable interspinous processspacer implant of FIG. 7B in a partial expanded position;

FIG. 7D is a perspective view of the expandable interspinous processspacer implant of FIG. 7C in a partial expanded position; and

FIG. 7E is a perspective view of the expandable interspinous processspacer implant of FIG. 7D in a fully expanded position.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” or “distally” and “outwardly” or “proximally” refer todirections toward and away from, respectively, the patient's body, orthe geometric center of the interspinous spacer implant and relatedparts thereof. The words, “anterior”, “posterior”, “superior,”“inferior” and related words and/or phrases designate preferredpositions and orientations in the human body to which reference is madeand are not meant to be limiting. The terminology includes theabove-listed words, derivatives thereof and words of similar import.

In reference to FIGS. 1 and 2, an expandable interspinous process spacerimplant 10 that is configured to be inserted into a space definedbetween a spinous process 500 a of a superior vertebral body and aspinous process 500 b of an inferior vertebral body is provided. Theimplant 10 is described herein as extending horizontally along alongitudinal direction “L” and lateral direction “A”, and verticallyalong a transverse direction “T”. Unless otherwise specified herein, theterms “lateral,” “longitudinal,” and “transverse” are used to describethe orthogonal directional components of various components. It shouldbe appreciated that while the longitudinal and lateral directions areillustrated as extending along a horizontal plane, and that thetransverse direction is illustrated as extending along a vertical plane,the planes that encompass the various directions may differ during use.For instance, when the spacer implant 10 is implanted into a spacedefined between adjacent spinous processes such as spinous processes 500a and 500 b, the transverse direction T extends generally along thesuperior-inferior (or caudal-cranial) direction, while the plane definedby the longitudinal direction L and lateral direction A lie generally inthe anatomical plane defined by the anterior-posterior direction, andthe medial-lateral direction. Accordingly, the directional terms“vertical” and “horizontal” are used to describe the spacer implant 10and its components as illustrated merely for the purposes of clarity andillustration.

As shown in FIG. 1, the implant 10 is configured to be inserted into aspace defined between adjacent spinous processes such as spinousprocesses 500 a and 500 b. The implant 10 extends along a longitudinaldirection L from a proximal end P to a distal end D. In the embodimentillustrated, the longitudinal direction L may also be considered theinsertion direction. As shown in FIG. 2, the implant 10 includes asuperior housing 14, an inferior housing 18, and a distracting member 22disposed between the superior and inferior housings 14, 18. Byactivating (i.e. translating, rotating, etc.) or otherwise moving thedistracting member 22 from a first position to a second position, thesuperior and inferior housing 14, 18 will be distracted apart from oneanother and the implant will be converted from a first or insertion orcollapsed configuration to a second or expanded configuration. In theillustrated embodiment, the distracting member 22 is an oblong cammember 24 that is configured to be rotated, such that upon a 90 degreerotation, the superior and inferior housings 14, 18 are distracted apartfrom one another to thereby distract the adjacent spinous process apartfrom one another.

As shown in FIGS. 2-6, the superior housing 14 includes a body 28 thatdefines an upper, or superior, or outer, engagement surface 30 that isconfigured to contact the spinous process of the superior vertebralbody, and a lower, or inferior, surface 34 that defines a void 38configured to at least partially house the cam member 24. The body 28further defines a proximal side 42, a distal side 46, and opposinglateral sides 50 that join the proximal side 42 and distal side 46.

As shown in FIG. 2, the upper surface 30 of the superior housing 14defines a notch 54 that extends transversely across a middle portion ofthe upper surface 30. The notch 54 is configured to engage and receivethe spinous process of the superior vertebral body when the implant 10is in an expanded configuration. Such a configuration helps align andsecure the implant 10 within the space between the adjacent spinousprocesses.

As best shown in FIGS. 4 and 6, the void 38 extends vertically into theinferior surface 34 of the superior housing 14 and along the inferiorsurface 34 in the longitudinal direction L. As best shown in FIG. 5, thevoid 38 is oblong in the lateral direction A and is configured to housethe oblong cam member 24. Furthermore, the void 38 defines a recess 60that is configured to be engaged by a protrusion extending from the cammember 24 when the cam member 24 has been moved from the first positionto the second position.

Similarly, the inferior housing 18 includes a body 68 that defines alower, or inferior, or outer, engagement surface 70 that is configuredto contact the spinous process of the inferior vertebral body, and anupper, or superior, surface 74 that defines a void 78 configured to atleast partially house the cam member 24. The body 68 further defines aproximal side 82, a distal side 86, and opposing lateral sides 90 thatjoin the proximal side 82 and distal side 86.

As shown in FIG. 2, the lower surface 70 of the inferior housing 18defines a notch 104 that extends transversely across a middle portion ofthe lower surface 70. The notch 104 is configured to engage and receivethe spinous process of the inferior vertebral body when the implant 10is in the expanded configuration. Such a configuration helps align andsecure the implant 10 within the space between the adjacent spinousprocesses.

As shown in FIGS. 4-6, the void 78 extends vertically into the superiorsurface 74 of the inferior housing 18 and along the inferior surface 34in the longitudinal direction L. As best shown in FIG. 4, the void 78 isoblong in the lateral direction A and is configured to house the oblongcam member 24. In particular, the void 38 defined in the superiorhousing 14 and the void 78 defined in the inferior housing 18, togetherdefine a cavity 114 that encapsulates the oblong cam member 24.Furthermore, the void 78 defines a recess 118 that is configured to beengaged by a protrusion extending from the cam member 24 when the cammember 24 has been moved from the first position to the second position.As shown in FIG. 6, the recess 118 of the void 78 opposes the recess 60of the void 38.

As shown in FIGS. 4-6, the cam member 24 is encapsulated within thecavity 114 defined by the voids 38, 78 of the superior and inferiorhousings 14, 18, and is configured to distract the superior and inferiorhousings 14, 18 away from each other when moved from the first positionto the second position. The cam member 24 defines a first pair ofopposed surfaces 119 that define a first distance D1 therebetween and asecond pair of opposed surfaces 120 that defined a second distance D2therebetween. The second pair of opposed surfaces 120 are angularlyoffset with respect to the first pair of opposed surfaces 119 by 90degrees, and the second distance D2 is greater than the first distanceD1.

As shown in FIG. 6, the cam member 24 is oblong in the lateral directionwhen in the first position. That is, the first opposed surfaces 119 ofthe cam member 24 engage the housings 14, 18, when the superior andinferior housings 14, 18 have not been distracted apart from each other.When the cam member 24 has been rotated to the second position the cammember is oblong in the transverse direction and the opposed secondsurfaces 120 engage the housings 14, 18 to thereby cause the housings14, 18 to distract from each other.

Also shown in FIG. 6, the second opposed surfaces 120 define curvedlateral ends 126. Extending laterally outward from each lateral end 126is a protrusion 130 that is configured to engage a respective recess 78,118 defined in the voids 38, 78 of the superior and inferior housings14, 18. During insertion of the implant 10, the cam member 24 is oblongin the lateral direction as shown in FIG. 6, and the protrusions 130extend laterally outward. When the cam member 24 is rotated 90 degrees,as shown in FIG. 5, the protrusions 130 extend transversely outward andwill engage the respective recesses 78, 118 defined in the housing voids38, 78 to thereby lock the implant 10 in the expanded configuration. Itshould be understood that the protrusions 130 may extend out from thecam member 24 anywhere along its length. For example, the protrusions130 may be angularly offset from each other by 90 degrees.

As shown in FIG. 6, a proximal end of the cam member 24 defines aninstrument engagement feature 122 that extends longitudinally into thecam member 24. The instrument engagement feature 122 may define a starthat is configured to receive a star drive, such that rotation of thestar drive rotates the cam member 24 to thereby move the cam member 24from the first position to the second position.

As best shown in FIGS. 2 and 4, the superior and inferior housings 14,18 provide access to the instrument engagement feature 122 of the cammember 24 when the implant 10 is in the collapsed configurations. Inthat regard, the superior housing 14 further defines a superiorsemi-cylindrical groove 180 that extends into the proximal side 42 ofthe superior housing 14 and into the void 38 of the superior housing 14,while the inferior housing 18 further defines an inferiorsemi-cylindrical groove 184 that extends into the proximal side 82 ofthe inferior housing and into the void 78 of the inferior housing 18. Asshown in FIG. 2, the superior semi-cylindrical groove 180 and theinferior semi-cylindrical groove 184 combine to form an access bore 188when the implant 10 is in a collapsed configuration. The access bore 188is configured to provide access for the driver instrument so that theinstrument can engage the instrument engagement feature 122 of the cammember 24 to thereby insert the implant 10 and activate or otherwisemove the cam member 24 once the implant is properly positioned.

As best shown in FIGS. 3A and 3B, the superior and inferior housings 14,18 further define oblong slots that are defined in their lateral sides.As shown, the superior housing 14 includes a first superior oblong slot210 that extends in the longitudinal direction L along a first lateralside 50 of the superior housing 14 and a second superior oblong slot 214that extends in the longitudinal direction L along a second lateral side50 of the superior housing 14. The first slot 210 extends distally alongthe first lateral side 50 from a point that is proximate to the proximalend 42 of the housing 14 to a point that is proximate to a midline ofthe housing 14. The second slot 214 extends distally along the secondlateral side 50 from a point that is proximate to the midline of thehousing 14 to a point that is proximate to the distal end 46 of thehousing 14. The slots 210 and 214 are configured to act as guidancetracks for their respective wing members.

Similarly, the inferior housing 18 includes a first inferior oblong slot218 that extends in the longitudinal direction L along a first lateralside 90 of the inferior housing 18 and a second inferior oblong slot 222that extends in the longitudinal direction L along a second lateral side90 of the inferior housing 18. The first slot 218 extends distally alongthe first lateral side 90 from a point that is proximate to a midline ofthe housing 18 to a point that is proximate to the distal end 86 of thehousing 18. The second slot 222 extends distally along the secondlateral side 90 from a point that is proximate to the proximal end 82 ofthe housing 18 to a point that is proximate to the midline of thehousing 18. The slots 218 and 222 are configured to act as guidancetracks for their respective wing members.

As shown in FIGS. 3A and 3B, the implant 10 further includes astabilizer 240 that comprises a plurality of deployable wing membersthat are rotatably coupled to one of the superior and inferior housings14, 18, and translatably coupled to the other of the superior andinferior housings 14, 18. The stabilizer is configured to engagerespective spinous processes of the superior and inferior vertebralbodies when the implant 10 is in an expanded configuration. As shown inFIGS. 3A and 3B, the implant 10 includes a first wing member 250 havinga body 254 that defines a superior end that is rotatably coupled to thesuperior housing 14 proximate to a distal end of the superior housing'sfirst slot 210. The first wing member 250 is rotatably coupled to thesuperior housing 14 with a first securement pin 260. A middle portion ofthe first wing member 250 is translatably coupled to the first slot 218of the inferior housing 18 with a first guidance pin 264. When thesuperior and inferior housings 14, 18 are distracted apart, the firstwing member 250 rotates counterclockwise about the securement pin 260and translates proximally or is otherwise guided within the first slot218. Once fully distracted, a first extension portion 268 of the firstwing member 250 protrudes from or otherwise extends below the inferiorsurface of the inferior housing 18.

The implant 10 further includes a second wing member 270 having a body274 that defines a superior end that is rotatably coupled to thesuperior housing 14 proximate to a proximal end of the superiorhousing's second slot 214. The second wing member 270 is rotatablycoupled to the superior housing 14 with a second securement pin 280. Amiddle portion of the second wing member 270 is translatably coupled tothe second slot 222 of the inferior housing 18 with a second guidancepin 284. When the superior and inferior housings 14, 18 are distractedapart, the second wing member 270 rotates clockwise about the securementpin 280 and translates distally or is otherwise guided within the secondslot 222. Once fully distracted a second extension portion 288 of thesecond wing member 270 protrudes from or otherwise extends below theinferior surface of the inferior housing 18.

The implant 10 further includes a third wing member 290 having a body294 that defines an inferior end that is rotatably coupled to theinferior housing 18 proximate to a proximal end of the inferiorhousing's first slot 218. The third wing member 290 is rotatably coupledto the inferior housing 18 with a third securement pin 300. A middleportion of the third wing member 290 is translatably coupled to thefirst slot 210 of the superior housing 14 with a third guidance pin 304.When the superior and inferior housings 14, 18 are distracted apart, thethird wing member 290 rotates counterclockwise about the securement pin300 and translates distally or is otherwise guided within the first slot210. Once fully distracted a third extension portion 308 of the thirdwing member 290 protrudes from or otherwise extends above the superiorsurface of the superior housing 14.

The implant 10 further includes a fourth wing member 320 having a body324 that defines an inferior end that is rotatably coupled to theinferior housing 18 proximate to a distal end of the inferior housing'ssecond slot 222. The fourth wing member 320 is rotatably coupled to theinferior housing 18 with a fourth securement pin 330. A middle portionof the fourth wing member 320 is translatably coupled to the second slot214 of the superior housing 14 with a fourth guidance pin 334. When thesuperior and inferior housings 14, 18 are distracted apart, the fourthwing member 320 rotates clockwise about the securement pin 330 andtranslates proximally or is otherwise guided within the second slot 214.Once fully distracted a fourth extension portion 338 of the fourth wingmember 320 protrudes from or otherwise extends above the superiorsurface of the superior housing 14.

As shown in FIG. 4, when the implant 10 is in an expanded configurationthe first extension 268 of the first wing member 250 and the secondextension 288 of the second wing member 270 protrude from and extendbelow the inferior surface of the inferior housing 18. As shown, thefirst and second extensions 268, 288 define a gap 370 that is configuredto receive the spinous process of the inferior vertebral body. In thisway, the first and second wing members 250, 270 engage the spinousprocess to thereby hold the implant 10 firmly in place.

Similarly, when the implant 10 is in an expanded configuration the thirdextension 308 of the third wing member 290 and the fourth extension 338of the fourth wing member 320 protrude from and extend above thesuperior surface of the superior housing 14. As shown, the third andfourth extensions 308, 338 define a gap 380 that is configured toreceive the spinous process of the superior vertebral body. In this way,the third and fourth wing members 290, 320 engage the spinous process tothereby hold the implant 10 firmly in place.

As shown in FIGS. 2-6, the implant 10 further includes cover plates tocover the wing members. As shown, the implant 10 includes a superiorfirst lateral side surface cover plate 390 and a superior second lateralside surface cover plate 396 that are each configured to couple to thefirst and second lateral sides, respectively, of the superior housing14. Similarly, the implant 10 includes an inferior first lateral sidesurface cover plate 400 and an inferior second lateral side surfacecover plate 404 that are configured to couple to the first and secondlateral sides, respectively, of the inferior housing 18. The coverplates 390, 396, 400, and 404 may shield the wing members from anydebris that may prevent them from functioning.

When the cover plates 390, 396, 400, and 404 are attached to the lateralsides of their respective housing bodies, openings are provided for thewing members to extend through when the implant is in an expandedconfiguration. As shown in FIG. 4, a first superior opening 408 isprovided between the first lateral side of the superior housing body 28and the superior first lateral side cover plate 390, and a secondsuperior opening 412 is provided between the second lateral side of thesuperior housing body 28 and the superior second lateral side coverplate 396. The openings 408 and 412 are configured to allow the superiorends of the third wing member 290 and the fourth wing member 320 todeploy therethrough upon expansion of the implant 10.

Similarly, a first inferior opening 420 is provided between the firstlateral side of the inferior housing body 68 and the inferior firstlateral side cover plate 400, and a second inferior opening 424 isprovided between the second lateral side of the inferior housing body 68and the inferior second lateral side cover plate 404. The openings 420and 424 are configured to allow the inferior ends of the first wingmember 250 and the second wing member 270 to deploy therethrough uponexpansion of the implant 10.

Referring back to FIG. 2, the distal sides 46, 86 of the superiorhousing 14 and the inferior housing 18 are tapered such that the implant10 is provided with a bullet-nosed tip 440 when the implant is in acollapsed configuration. In particular, the distal side 46 of thesuperior housing 14 includes a distraction surface 444 that anglestransversely out as it extends proximally. Similarly, the distal side 86of the inferior housing 18 includes a distraction surface 448 thatangles transversely out as it extends proximally. Such a design helps toease the insertion of the implant 10 into the interspinous space as wellas to provide an initial amount of distraction to the adjacent spinousprocesses.

In operation, and in reference to FIGS. 7A-7E, adjacent spinousprocesses 500 a and 500 b between which the treatment of spinal stenosisis desired are identified and an incision is made in the back of thepatient. In one embodiment, the incision is made to accommodate alateral approach, although it should be understood that a variety ofapproach angles are appropriate for use with the present implant. Asshown in FIG. 7A, the distal end of an instrument 510 is inserted intothe access opening 188 defined by the collapsed implant housings 14, 18and is mated with or otherwise engages the instrument engagement feature122 defined by the cam member 24, to thereby couple the implant 10 tothe instrument 510. While in a collapsed configuration, the wing membersare for the most part are not protruding from the housings 14, 18, andthe implant 10 is inserted into the space defined between the adjacentspinous processes 500 a, 500 b using the instrument 510. Thebullet-nosed distal tip of the implant 10 eases the insertion and mayprovide an amount of distraction to the spinous processes 500 a, 500 bduring insertion.

Once the surgeon determines that the implant 10 is disposed at a desiredposition between the adjacent spinous processes 500 a, 500 b, and theinferior surface of the superior spinous process 500 a is disposedwithin the notch 54 defined in the superior housing 14, and the superiorsurface of the inferior spinous process 500 b is disposed within thenotch 104 defined by the inferior housing 18, e.g., using fluoroscopy ora CT scan, the instrument 510 is rotated 90 degrees, which therebyrotates the cam member 24 from the first position to the second positionand distracts the superior housing 14 away from the inferior housing 18.Once the cam member 24 has been moved to the second position, orotherwise turned 90 degrees, the first and second cam protrusions 130engage the first and second recesses 78, 118 of the superior andinferior housing voids, respectively to lock the implant 10 in itsexpanded configuration.

As shown in FIGS. 7B-7D, during the expansion of the implant 10 causedby the rotation of the cam member 24 by the instrument 510, the firstwing 250, the second wing 270, the third wing 290, and the fourth wing320 automatically deploy through the first inferior opening 420, thefirst superior opening 408, the second inferior opening 424, and thesecond superior opening 412, respectively. That is, the first wing 250,the second wing 270, the third wing 290, and the fourth wing 320articulate about their respective securement pins 260, 280, 300, and330, as they translate within their respective guidance tracks or slots218, 222, 210, and 214 to thereby protrude outward from the housings 14and 18 as shown in FIG. 7D. Once the implant 10 assumes its expandedconfiguration, the first, second, third, and fourth wings 250, 270, 290,and 320 secure the implant 10 with respect to the adjacent spinousprocesses 500 a, 500 b and the instrument 510 is disengaged from the cammember 24 and removed as shown in FIG. 7E.

The components of the implant 10 are formed from implant-grade plasticssuch as PEEK or ultra high molecular weight polyethylene (UHMWPE);however, a variety of biocompatible materials such as titanium and itsalloys, stainless steel, cobalt-chromium, biocompatible polymers, andbone material such as allograft can be utilized to form one or more ofthe components of the implant 10. Further, a combination of materialscan be envisioned as suitable for forming the implant 10, such as theinclusion of PEEK to form the superior and inferior housings 14, 18 andthe inclusion of titanium to form the distraction member 22 and thewings 250, 270, 290, and 320. Further, depending upon the choice ofmaterials used to form the implant 10 and its various components, theimplant 10 may provide expansion on a continuum from soft and flexibleto completely rigid. There may further be a dampening or cushioningcomponent disposed within the implant 10 that provides a desired amountof flexibility with a stop element to prevent deflection of the implant10 beyond a predetermined limit.

It should be understood that the distraction member may include avariety of designs that could expand the implant to its expandedconfiguration. For example, in an alternate embodiment, the distractingmember 22 can be replaced with a wedge member that can be pulled orpushed into matching wedge-shaped recesses defined on the inferiorsurface of the superior housing 14 and/or the superior surface of theinferior housing 18 to thereby expand the implant 10. In yet anotheralternate embodiment, the distracting member 22 can be replaced with aturnbuckle that, upon rotation about a vertical axis, distracts thesuperior and inferior housings 14, 18. In yet another alternateembodiment, the distracting member 22 can be replaced with a pluralityof camming elements that rotate in the same or opposite directions. Sucha plurality of camming elements may include features that couple thecamming elements' motion in order to add stability to the implant in itsexpanded configuration. In yet another alternate embodiment, thedistracting member 22 can be replaced with a member featuring conicalmale threads mating with conical female threads on the insides of thesuperior housing 14 and the inferior housing 18.

It should also be understood that the implant 10 may include any numberof wings and is not limited to four wings as shown in the illustratedembodiment. For example, the implant 10 may have additional wings thatmay be disposed, for example, at the center of the implant 10. In yetanother embodiment, only two wings may be included in the design.Further the wings do not have to rotate as shown. For example, theimplant 10 may include a pair of fixed wings on a first side of theimplant 10 and a pair of deployable wings on a second side of theimplant 10.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. Furthermore, it should be appreciated thatthe structure, features, and methods as described above with respect toany of the embodiments described herein can be incorporated into any ofthe other embodiments described herein unless otherwise indicated. It isunderstood, therefore, that this invention is not limited to theparticular embodiments disclosed, but it is intended to covermodifications within the spirit and scope of the present disclosure.

1. An expandable interspinous spacer implant configured to be insertedinto an interspinous space that is defined between a spinous process ofa superior vertebral body and a spinous process of an inferior vertebralbody, the implant comprising: a superior housing having an outer surfaceconfigured to engage the spinous process of the superior vertebral body;an inferior housing having an outer surface configured to engage thespinous process of the inferior vertebral body; and a distracting memberrotatably disposed between the superior and inferior housings, thedistracting member defining a first pair of opposed surfaces that definea first distance therebetween, and a second pair of opposed surfacesangularly offset with respect to the first pair of opposed surfaces, thesecond pair of opposed surfaces defining a second distance therebetweenthat is greater than the first distance.
 2. The implant of claim 1,wherein rotation of the distracting member such that the second opposedsurfaces operatively engage the superior and inferior housings causesthe superior and inferior housings to distract from each other.
 3. Theimplant of claim 1, wherein the distracting member is encapsulated in avoid defined by at least one of the superior and inferior housings. 4.The implant of claim 1, wherein the superior and inferior housings eachinclude a proximal side, and the proximal sides of the superior andinferior housings together define a bore that provides access to aninstrument engagement feature defined by the distracting member.
 5. Theimplant of claim 1, wherein (i) an inferior surface of the superiorhousing defines a first recess, and a superior surface of the inferiorhousing defines a second recess, (ii) the distracting member definesopposed protrusions, and (iii) the protrusions engage the first andsecond recesses when the superior and inferior housings are fullydistracted apart.
 6. The implant of claim 1, further comprising astabilizer that protrudes from at least one of the superior and inferiorhousings when the superior and inferior housings are fully distractedapart.
 7. The implant of claim 6, wherein the stabilizer comprises aplurality of deployable wing members, each wing member rotatably coupledto either the superior housing or the inferior housing.
 8. The implantof claim 7, wherein a portion of each wing member is translatably guidedthrough a respective guidance track that is defined by one of thesuperior housing and the inferior housing.
 8. The implant of claim 7,wherein (i) a first wing member is rotatably coupled to a first side ofthe superior housing and is translatably guided through a first guidancetrack defined in a first side of the inferior housing, (ii) a secondwing member is rotatably coupled to a second side of the superiorhousing and is translatably guided through a second guidance trackdefined in a second side of the inferior housing, (iii) a third wingmember is rotatably coupled to the first side of the inferior housingand is translatably guided through a third guidance track defined in thefirst side of the superior housing, and (iv) a fourth wing member isrotatably coupled to a second side of the inferior housing and istranslatably guided through a fourth guidance track defined in thesecond side of the superior housing.
 9. The implant of claim 8, whereinrotation of the distracting member causes the first, second, third, andfourth wing members to rotate and protrude from the superior andinferior housings.
 10. The implant of claim 1, wherein the distractingmember is an oblong cam member.
 11. The implant of claim 1, wherein theouter surfaces of the superior and inferior housings define transversenotches that are configured to receive respective spinous processes. 12.An expandable interspinous spacer implant configured to be inserted intoan interspinous space that is defined between a spinous process of asuperior vertebral body and a spinous process of an inferior vertebralbody, the implant comprising: a superior housing having an outer surfaceconfigured to engage the spinous process of the superior vertebral body;an inferior housing having an outer surface configured to engage thespinous process of the inferior vertebral body; and a deployable wingmember rotatably coupled to the superior housing and translatably guidedthrough a guidance track defined by the inferior housing.
 13. Theimplant of claim 12, wherein the deployable wing member is a first wingmember that is rotatably coupled to a first side of the superior housingand translatably guided through a guidance track defined by a first sideof the inferior housing.
 14. The implant of claim 13, further comprisinga second deployable wing member rotatably coupled to a second side ofthe superior housing and translatably guided through a guidance trackdefined by a second side of the inferior housing, (ii) a thirddeployable wing member rotatably coupled to a first side of the inferiorhousing and translatably guided through a guidance track defined by afirst side of the superior housing, and (iii) a fourth deployable wingmember rotatably coupled to a second side of the inferior housing andtranslatably guided through a guidance track defined by a second side ofthe superior housing.
 15. The implant of claim 14, wherein the first,second, third, and fourth wing members are deployed as the superior andinferior housings are distracted apart from each other.
 16. The implantof claim 14, further comprising a first cover that covers the first sideof the superior housing, a second cover that covers the second side ofthe superior housing, a third cover that covers the first side of theinferior housing, and a fourth cover that covers the second side of theinferior housing.
 17. The implant of claim 12, further comprising adistracting member disposed between the superior and inferior housings,wherein movement of the distracting member from a first position to asecond position distracts the superior and inferior housings apart fromeach other.
 18. The implant of claim 17, wherein the superior andinferior housings each include a proximal side, and the proximal sidesof the superior and inferior housings together define a bore thatprovides access to an instrument engagement feature defined by thedistracting member.
 19. The implant of claim 17, wherein (i) thedistracting member defines a first pair of opposed surfaces that definea first distance therebetween, and a second pair of opposed surfacesangularly offset with respect to the first pair of opposed surfaces, thesecond pair of opposed surfaces defining a second distance therebetweenthat is greater than the first distance, and (ii) rotation of thedistracting member distracts the superior and inferior housings apartfrom each other.
 20. The implant of claim 17, wherein (i) an inferiorsurface of the superior housing defines a first recess, and a superiorsurface of the inferior housing defines a second recess, (ii) thedistracting member defines opposed protrusions, and (iii) theprotrusions engage the first and second recesses when the superior andinferior housings are fully distracted apart.
 21. An expandableinterspinous spacer implant configured to be inserted into aninterspinous space that is defined between a spinous process of asuperior vertebral body and a spinous process of an inferior vertebralbody, the implant comprising: a superior housing having an outer surfaceconfigured to engage the spinous process of the superior vertebral body;an inferior housing having an outer surface configured to engage thespinous process of the inferior vertebral body; a distracting memberdisposed between the superior and inferior housings, wherein movement ofthe distracting member from a first position to a second positiondistracts the superior and inferior housings apart from each other; andat least one wing member having an extension, the wing member rotatablycoupled to a respective one of the superior and inferior housings, suchthat movement of the distraction member from the first position to thesecond position causes the at least one wing member to rotate about therespective housing to thereby cause the extension to extend out arespective housing.
 22. The implant of claim 21, wherein (i) thedistracting member defines a first pair of opposed surfaces that definea first distance therebetween, and a second pair of opposed surfacesangularly offset with respect to the first pair of opposed surfaces, thesecond pair of opposed surfaces defining a second distance therebetweenthat is greater than the first distance, and (ii) rotation of thedistracting member causes the superior and inferior housings to distractapart from each other.
 23. The implant of claim 21, wherein the superiorand inferior housings each include a proximal side, and the proximalsides of the superior and inferior housings together define a bore thatprovides access to an instrument engagement feature defined by thedistracting member.
 24. The implant of claim 21, wherein (i) an inferiorsurface of the superior housing defines a first recess, and a superiorsurface of the inferior housing defines a second recess, (ii) thedistracting member defines opposed protrusions, and (iii) theprotrusions engage the first and second recesses when the superior andinferior housings are fully distracted apart.
 25. The implant of claim30, wherein (i) a first deployable wing member is rotatably coupled to afirst side of the superior housing and translatably coupled to aguidance track defined by a first side of the inferior housing, (ii) asecond deployable wing member is rotatably coupled to a second side ofthe superior housing and translatably coupled to a guidance trackdefined by a second side of the inferior housing, (iii) a thirddeployable wing member is rotatably coupled to a first side of theinferior housing and translatably coupled to a guidance track defined bya first side of the superior housing, and (iv) a fourth deployable wingmember is rotatably coupled to a second side of the inferior housing andtranslatably coupled to a guidance track defined by a second side of thesuperior housing.
 26. The implant of claim 25, wherein (i) the first andsecond deployable wing members rotate and engage the spinous process ofthe inferior vertebral body when the superior and inferior housings aredistracted apart from each other, and (ii) the third and fourthdeployable wing members rotate and engage the spinous process of thesuperior vertebral body when the superior and inferior housings aredistracted apart from each other.
 27. The implant of claim 25, furthercomprising a first cover that covers the first side of the superiorhousing, a second cover that covers the second side of the superiorhousing, a third cover that covers the first side of the inferiorhousing, and a fourth cover that covers the second side of the inferiorhousing.